The present invention relates in general to electrochemical energy sources, and more particularly to impregnating a battery cell with a liquid electrolyte.
A battery cell may include one or more sub assemblies known as cell stacks. The number of cell stacks that form the cell depends on the particular application. Each cell stack is formed by stacking plates together. For example, a central foil plate may be sandwiched between a pair of polymer plates, and the polymer plates may be sandwiched between a pair of outer foil plates. It is to be appreciated, however, that the plate materials and stack arrangements vary according to the particular application.
Conventionally, the cell stacks are assembled together to form cells. The cells are then packaged or assembled in a battery casing. Subsequently, the cells are activated by introducing a liquid electrolyte into the cell. Various techniques are used to fill the cells with the electrolyte. These techniques include pouring the electrolyte from a holding container into a cell filling port, and squirting the electrolyte into the cell using a squeeze bottle or syringe. It is also known to provide a flexible container as part of the battery housing to store the electrolyte prior to its dispersal into the battery cells.
Although these conventional techniques are generally thought to be acceptable, they are not without shortcomings. In particular, the devices that discharge the electrolyte are cumbersome and unreliable. For example, during the filling process, electrolyte may inadvertently contaminate the opening of the package in which the cell is disposed. The electrolyte on the opening compromises the seal that is subsequently provided to close the package opening. Also, conventional filling techniques do not provide adequate control over electrolyte uptake, and they require a significant amount of electrolyte that is not absorbed.
It is an object of this invention to provide a fixture and a method for liquid electrolyte impregnation of a battery cell that provides 1) improved package reliability, 2) improved control over electrolyte delivery and uptake, and 3) reduced electrolyte consumption.
The invention resides in a fixture for fabricating an electrochemical cell. The fixture includes an enclosure with a nest that is shaped to receive the electrochemical cell therein. The enclosure is provided with a fill port that is in communication with the nest. The fill port provides a passage through which an electrolyte is injected into the nest. The fill port may also provide a passage through which a vacuum is applied to the electrochemical cell. In an alternative embodiment, the enclosure is provided with two dedicated ports: a fill port through which the electrolyte is injected; and a vacuum port through which a vacuum is pulled.
The invention also resides in a method for fabricating an electrochemical cell. First, the cell is placed in an enclosure which is not a part of the battery. A vacuum is then applied to the enclosure. And finally, a liquid electrolyte is introduced into the enclosure, thereby impregnating the electrochemical cell with electrolyte.
The above and other features of the invention including various and novel details of construction and process steps will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular apparatus and method for liquid electrolyte impregnation of a battery cell embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.